sub make_key {
  my $sn = shift;
  my $tag = $my_server_hash{$sn}{tag};

  # NOTE: presumes largest server name may be contained
  # in 20 chars and that {tag} values won't exceed 99,999
  return sprintf "%1d%20s%5d", ($tag == 53), $sn, $tag};
}

sub decode_key {
  my $key = shift;
  return substr $key, 1, 20;
}

my @server_names = map { decode_key($_) }
                   sort { $a cmp $b }
                   map { make_key($_) } keys %my_server_hash;